As pointed out at length in McSherry et al U.S. Pat. No. 4,075,924, the prior practice of constructing building walls of plaster backed by wire or wood laths, produced substantial relatively massive wall structures capable of supporting or mounting relatively heavy objects by relatively uncomplicated fasteners attachable to walls by screws, bolts, nails and the like. However, the more modern building construction technique is to construct walls and partitions of wallboard panels. Commonly referred to as dry or hollow wall, the technique uses panels of materials such as plasterboard and beaverboard, and secures them without intermediate backing to horizontally spaced wood studs. Structurally thin and weak relative to plaster walls, plasterboard and like panels between studs are incapable, with fasteners suited for plaster walls, of sustaining substantial loads for any but brief intervals.
The economic advantages of dry or hollow wall over plaster wall construction has led to the development of innumerable blind wall fasteners for use on panels inaccessible from the back. Usually of the toggle type, with a winged or straight crosspiece threaded or threadable to a toggle bolt and insertible either folded against or disposed parallel to the bolt through an opening in the panel and then, as in the above McSherry patent, manipulated by attached arms or other usually flexible means to a position in which the crosspiece extends along the back of the panel perpendicular to the bolt.
An earlier Fischer, U.S. Pat. No. 3,211,042, resembles McSherry in having a preformed threaded central bore in its crosspiece for receiving a screw and means attached to the crosspiece for inserting it through a wall opening and then positioning it along the back of the wall.
With their common features preformed threaded bores in their crosspieces and means attached to and inserted with the crosspieces for positioning them along the backs of the wall panels, the Shamah, U.S. Pat. No. 4,286,497 is exemplary of a blind wall fastener of the foldable wing type, while the patent to McSherry U.S. Pat. No. 4,294,156 is basically the same and an improvement on his earlier U.S. Pat. No. 4,075,924.
While in essence toggles adapted by their crosspieces to sustain relatively heavy loads, the blind wall fasteners of the above patents are ill-adapted to support or mount on hollow or dry wall panels fixtures or articles, such as brackets, towel bars and paper holders, secured by screws to drilled-in-situ blind anchor plates . It is with the mounting on hollow or dry wall panels of fixtures of this type that the present invention is particularly concerned.